Direct observations and measurent of the microcirculation will be used to study the behavior of degradable starch microspheres following intraarterial injection. The ischemia produced by the intraarterial injection of these micro-spheres could have two potential uses. The first would be to increase the local concentration of a drug by transiently trapping the drug in the microcirculation. Secondly, the transient ischemia produced by intraarterial injection of the microspheres could be used to protect healthy tissue during radiation therapy. The circulatory parameters which influence microsphere distribution will be examined. The effects of microsphere injection on exchange across the blood vessels will also be examined.